A/C Compressor Clutch

WARNING: This page is about a different car, the 2003 Pontiac Sunfire, 2003 Pontiac Grand Am, 2003 Oldsmobile Alero, and 2003 Chevrolet Cavalier. However, it is still accessible from the selected car via links, so may be relevant.

On many models, PCM regulates operation of A/C compressor clutch through a PCM-controlled A/C compressor clutch relay. This allows the PCM to disengage the A/C compressor when compressor load on engine may cause driveability problems (i.e., during hot restart, idle, low speed steering maneuvers and wide open throttle operation), or if A/C refrigerant pressure drops or rises beyond normal operating levels.

Ignition voltage is supplied directly to the A/C compressor clutch relay. The Powertrain Control Module (PCM) controls the relay by grounding the control circuit via an internal solid state device called a driver. The primary function of the driver is to supply the ground for the component being controlled. Each driver has a fault line which is monitored by the PCM. When the PCM is commanding a component ON, the voltage of the control circuit should be near zero volts. When the PCM is commanding the control circuit to a component OFF, the voltage potential of the circuit should be near battery voltage. If the fault detection circuit senses a voltage other than what is expected, the PCM will set a DTC.

Refrigerant pressure sensing may be accomplished by monitoring high and low pressure switches or a pressure sensor which will register either high or low pressure levels. Power steering load is monitored through a power steering pressure switch. Hot restart is monitored through the coolant temperature sensor. For component application and related wiring, see appropriate article in AIR CONDITIONING & HEATING. For related wiring, see AIR CONDITIONING in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL.